This invention relates to solder or pure metal preforms for use in joining one object to another, and more particularly to an integrated preform for joining electronic elements to connectors, circuit boards, terminals and other elements.
The art of soldering is old, and the techniques that have been developed over the years are as varied as the types of apparatus which must be soldered. Increasingly, particularly in the field of electronics, many multiple element structures must be rapidly and automatically joined together without disturbing parts alignment.
Various solder preforms have been suggested such as those in U.S. Pat. No. 4,050,621 to Bouley and U.S. Pat. No. 4,557,411 to Farquharson. In these patents, clusters are shown in which a series of solder islands are joined together by narrow bridging bands of solder material in a pattern to match a similar pattern on a circuit board or the like. In one embodiment, the solder islands are washer-type elements having holes that align with similar holes in the circuit board and component pins are passed through the aligned holes. The assembly is heated to a desired temperature to melt the solder. The solder in the bridging bands flows into the adjacent washers through means of a wicking action and a solder joint is formed between the component pins and the circuit board.
As suggested in the noted '411 patent, this preform matrix works well for certain applications. However, in other applications, the bridging bands may not be completely severed after melting, thereby causing defects in the finished product. In the electronics art today, very complicated and expensive components, circuit boards and other devices are fastened one to the other. When soldered, these components cannot be readily separated without causing considerable damage to the part and the part must be scraped or reworked. As is well known, scrapping or reworking of parts is generally expensive.
Processes wherein unbonded solder preforms are installed upon a circuit board or the like sometimes require extensive handling of the assembly before the final bonding operation is completed. The preform thus can become misaligned or dislodged from the assembly during the various handling operations.